Key Information

Vocabulary: Mendelian Genetics

Locus (pl. loci)

A place in a chromosome where a gene resides. Each locus contains the encoded information for a trait, such as "colour of the eyes".

Allele

Or allelomorph gene. Any of a number of the alternative varieties of a gene that reside in the same locus. Each allele contains the encoded information for a quality or a value of a trait, such as "brown colour of the eyes". All the possible alleles for the same locus form a "family of allelomorph genes".

Haploid

Cell or individual or species with one single set of chromosomes, such as bacteria or the human gametes.

Diploid

Cell or individual or species with two sets of chromosomes, such as the body cells of humans (and most eukaryotes). Each chromosome of a set is similar to one chromosome of the other set in that they carry exactly the same loci, but they are not identical, as the specific alleles of each locus can be different.

Homologous

In diploid individuals, each pair of chromosomes that carry the same loci. Humans have 22 pairs of homologous chromosomes and one pair (the sex chromosomes) which are partially homologous.

Homozygous

Or "pure breed". Diploid individuals are homozygous for a locus when the alleles present in that locus are the same in both homologous chromosomes.

Heterozygous

Or "hybrid". Diploid individuals are heterozygous for a locus when the alleles present in that locus are different in each homologous chromosome.

Dominance

A type of relationship between two different alleles of the same family whereby one allele (said to be the "dominant" one) cancels out the phenotypic effect of the other (said to be "recessive").

Codominance

A type of relationship between two different alleles of the same family whereby both alleles express their phenotypic effects without blending. This is the case of the alleles for the "A" and "B" human blood types, whose heterozygosis yields an "AB" type.

Incomplete dominance

A type of relationship between two different alleles of the same family whereby the phenotypic effects of each allele are blended in the phenotype. This is the case of the alleles for the red and white colour for the corolla of the flowers of the snapdragon plant, whose heterozygosis yields a pink colour.

Mind Map: First artificial cell

External Links

Miscellaneous

Learn Genetics.From the basics to the hottest current topics: a vast bank of easy to follow learning resources on Genetics.

Interactives: DNA.Excellent full lesson on DNA with interactive activities and good coverage of the following topics: genetics, discovery of DNA, Human Genome Project, Genetic Engineering, and implications and ethics.

Reproductive Biotechnology

Cloning.Simple and clear animation showing the main steps to take in animal cloning.

How cloning works.Simple and easy to understand introduction to cloning in plants, animals and humans.

How human cloning will work.Today, after more than a decade since Dolly, human cloning remains in its infancy and under governmental restraints. Nevertheless, science is headed in that direction. Learn how the inevitable human cloning future will be.

Beginning more than 3.5 billion years ago, a tiny, primitive molecule encoded instructions, that it passed to its children, who passed it to their children and so on, all the way down through time to all living things today. Watch the story of DNA.

Applied Genetics

Comprehensive video on the basic process of genetic engineering: creating recombinant DNA from different species.

18 genetically modified organisms you don't know about

From Glow in the Dark Rabbit to Anti-Cancer Purple Tomatoes, here are 18 Genetically Modified Organisms You Don't Know About.

Gene therapy

See how a virus can be recombined with human DNA to save the life of a person.

CRISPR: Gene editing and beyond

The CRISPR-Cas9 system has revolutionised gene-editing, but cutting DNA isn’t all it can do. From turning gene expression on and off to fluorescently tagging particular sequences, this animation explores some of the exciting possibilities of CRISPR.

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Inanimate objects can be classified scientifically into three major categories; those that don't work, those that break down and those that get lost.